Domestic type and size waste water treatments using SBR are known, being the most widely used embodiment in Germany.
The prior art provides several references of process operating with SBR systems, such as, document WO 95/09130 (Timpany) dated Apr. 6, 1995, disclosing a process for water and waste water treatment with substantially constant biological content, which would allow for an efficient waste water treatment, combining the advantages and removing disadvantages of both activated sludge and SBR processes. In this case, waste water flows continuously in one direction through a plurality of hydraulically connected treatment cells in series. Waste water is subject to biological treatment in at least one of the cells, and is housed in at least a last treatment and discharge cell, immediately before the system discharge. In subsequent steps, waste water can continue in order to be fed into the system, in the same location while the last cell is temporarily closed. The mixture aeration device is diverted there to resuspend housed mixture liquor suspended solids and provide additional treatment. A transfer pump is diverted there to transfer suspended solids in the mixture liquor and the partially treated waste water, jointly mixed back to a previous treatment cell, and when completing the transfer step, the mixture aeration device is diverted until allowing accommodation of biological solids before treated waste water discharge on a continuous basis. Mixed liquor suspended solids flow in the same general direction as the waste water, but it always receives at least partial retrotransfer up to a previous treatment cell, accommodating and separating remaining solids coming from waste water before the treated waste water discharge from the last cell. In addition, continuous discharges are included and constant level operation on an essentially full basis through use of two discharge cells alternatively, and treatment of soluble pollutants and particulate matter, as well as biological removal of nitrogen and phosphorus.
The document EP 0834474 (Holm) dated Jun. 13, 2001, describes a procedure for discontinuous waste water purification according to the activated sludge procedure, wherein the cycle strategy for SBRs provides at least two internal cycles. The first internal filling with supernatant is made from a storage tank preferably to obtain a biological P redisolution. Last internal fillings are made with sediment, preferably in order to produce denitrification. This procedure is characterized in that waste water from an intermediate tank, that can be used for splitting raw water and is fitted with a circulation device, is transported to at least an SBR with at least two internal cycles; during the stage consisting of filling the first internal cycle or the first internal cycles, a previously treated waste water that produces a little loaded surplus is transported from the intermediate tank to the SBR; at least during the last total cycle filling stage, an essentially lower amount of waste water substantially concentrated as a sediment is transported from the intermediate tank to the SBR; with circulation stopped, previously reclaimed waste water is extracted from the upper part of the intermediate tank; with circulation in operation, concentrated was water is taken from the intermediate tank, dragging a high sediment content, or concentrated waste water is obtained from the bottom of the intermediate tank, resulting thus in transport of almost exclusively sediment (eventually with a certain amount of surplus); and the amount of nitrate to be denitrified after the first or penultimate cycle is estimated directly or indirectly; this is used to estimated the amount/class of concentrated waste water for the last internal cycle. In this procedure, the filling stage and also eventually the subsequent pure circulation stage of the first internal cycle are used for biological removal of P, and the necessary duration of this stage is controlled/regulated by the corresponding meter device.
In general terms, the single household SBR systems consist of a tank divided into two parts, the first is intended to be used as a storage tank (also known as a lung tank), which is used to store domestic effluent until the time comes to load it into the aerated SBR (second part). In conventional systems, both the storage tank and the aerated SBR aeration compartment are simply built in bigger sizes in order to prevent overflows, resulting in higher construction costs, transport costs, and subsequent operation cost, because higher consumption of electric power is needed for air pumping in order to keep biological sludge in suspension. The system is commanded by a PLC that inalterably marks times of the main SBR process stages, such as, 1) charging the affluent into the SBR, 2) aeration of the SBR, 3) biology settling, 4) removal of supernatant clarified liquid, and 5) bleeding excessive sludge sending it back to the storage tank aeration compartment. Therefore, the conventional system does not include any function generated by any type of sensor that measures a variable, specially the level, and temporarily alters the initial logic program in order to obtain higher process efficiency. Prior art is well-known and can be found in the websites of many German and Austrian companies, such as, www.pwn.at; www.zapf-abs.de; www.graf-online.de
In single household SBR systems and in single household systems in general, the sludge age parameter does not have control mechanisms, due to which an amount of sludge lower than the production rate is removed, increasing thus the amount of sludge, also increasing the sludge age. This results in the loss of proper floc formation properties and therefore good settling capacity, often reaching the less desired condition, which is proliferation of filamentous sludge.
In addition, as a consequence of large reactor volumes used in currently used systems, very low food/microorganism ratios (F/M) are used, resulting in sludge with low settling and stability conditions, requiring an hour to settle, which on one hand reduces time available to add an additional operation cycle per day, and on the other hand does not allow approaching aerobic macro granulation (having low sludge volumetric indexes, around 30 ml/gr), or directly prevents such desirable condition, which is maximum reach of the field technique of on site selection of activated sludge microorganisms, with multiples operational advantages. Note that aerobic macro granulation is a sludge property only given by SBR systems. As a general optimization concept, it is always desirable that all processes are carried out in the smallest possible reactor, which would result in lower manufacture costs, as well as in transport and installation savings, and lower subsequent operation costs.
The geometry of currently used reactors does not allow transporting a large number of units in economic terms, because they cannot be transported one inside the other due to their internal divisions.
Currently used systems used not have a system allowing them reacting in case of emergency for excessive flow, different from simple overflow implying loss of biology by dragging. Therefore, in case of emergency, the do not have a partial evacuation system in small amounts of partially treated effluent, but making sure that biology is not lost.